Field of the Invention
The present invention relates to an illumination device, an exposure apparatus, an adjusting method, and a method for manufacturing an object.
Description of the Related Art
An exposure apparatus is used in a lithography process for manufacturing a semiconductor device, a liquid crystal display device, or the like. The exposure apparatus illuminates a mask (reticle) so that a pattern of the mask is transferred onto a substrate (wafer, glass plate, or the like), to which a photosensitive material (resist) is applied, through a projection optical system.
With regard to, for example, projection exposure apparatuses that transfer a pattern onto a glass plate, in recent years, there has been a demand for an exposure apparatus capable of performing full-plate exposure in which a pattern of a mask having a large area is transferred onto a substrate. To meet such a demand, a step-and-scan (scanning) projection exposure apparatus, with which high resolution can be achieved and a large area can be subjected to exposure, has been proposed. In the scanning exposure apparatus, the mask is illuminated with exposure light that has passed through a slit while the mask and the substrate are being moved. Thus, the pattern of the mask is transferred onto the substrate by scanning the substrate with the exposure light through the projection optical system.
Japanese Patent Laid-Open No. 2001-326171 describes a technology for increasing the energy of light for illuminating the mask to increase the productivity of the scanning exposure apparatus. More specifically, an illumination optical system is described in which light beams emitted from three light source units are incident on a collimator in such a manner that the light beams are arranged next to each other. The collimator superposes the light beams from the three light source units into light that illuminates the mask.
Japanese Patent Laid-Open No. 2008-262911 describes a light source unit in which part of light that is focused by an ellipsoidal mirror and travels toward a mask is blocked by an electrode line of a mercury lamp and a cooling nozzle that suppresses heating of the light source unit. It is also described that the electrode line of the light source unit and the cooling nozzle may be integrated together to reduce loss in the amount of light caused by the electrode line and the cooling nozzle in the light source unit.
When part of the light that is focused by the ellipsoidal mirror and that travels toward the mask is blocked by light blocking members, such as the electrode line of the light source unit and the cooling nozzle, shadows of the light blocking members are formed in a light intensity distribution (effective light source distribution) on a pupil plane of the illumination optical system, which is downstream of the light source unit.
In the case where a plurality of light source units are used for the exposure of the substrate, the shadows of the light blocking members included in the light source units may overlap in the effective light source distribution, and be collected in a region in a certain direction from the center of the effective light source distribution. In such a case, uniformity of the effective light source distribution is degraded. Therefore, there is a risk that a line width of a pattern formed on the substrate will be different from the desired value or be non-uniform, and there is also a risk that the resolution of the pattern will be reduced. In addition, the resolution will vary depending on the direction of the pattern of the mask. For example, consider a case in which a mask pattern including pattern elements that are arranged periodically in an X direction and pattern elements that are arranged periodically in a Y direction, which is perpendicular to the X direction, is illuminated. In such a case, when the shadows of the light blocking members extend only in the X direction in the effective light source distribution, line widths of the pattern elements projected onto the substrate differ between the X direction and the Y direction.
The above-described problems are not described in Japanese Patent Laid-Open No. 2001-326171 or Japanese Patent Laid-Open No. 2008-262911, and means for solving the problems is also not described.